A feature of many modem dangerous condition alarm units--such as smoke detectors, CO detectors, etc.--is that a multi-station system may be established by suitably interconnecting individual units. Thus, for example, a home may employ a plurality of smoke detectors distributed in a corresponding plurality of rooms with the individual smoke detectors interconnected such that an alarm condition sensed at any station results in all the smoke detectors sounding an alarm. This arrangement has the obvious advantage of providing an indication of an alarm condition sensed in another room which may be sufficiently remote from the present location of the inhabitants that the alarm might not otherwise be noticed until the condition which caused the alarm has progressed to a dangerous state. As a specific example, a fire originating in a kitchen at night and causing a smoke detector in the kitchen to sense the resulting presence of smoke will cause an alarm to sound in the bedrooms in which the occupants are asleep, thus awakening the occupants as soon as the alarm condition in the kitchen is sensed.
However, a defective unit may be among those constituting a multi-station dangerous condition alarm system. If a false alarm is initiated and the units are still within a warranty period, the owner may believe it is necessary to return all the units making up the system to the retailer or manufacturer because it cannot be easily determined which unit is defective. This is a costly problem for the manufacturer and also leaves the consumer without a dangerous condition alarm system, at least temporarily.
Similarly, most dangerous condition sensing units are either battery operated or incorporate battery back up if normally energized off the line. Typically, a battery condition monitoring feature is included in which an audible "chirp" is periodically issued if the voltage across the battery terminals has fallen below a predetermined level, thus indicating that the remaining battery life is short and that the battery should be replaced. Because of the character of the "chirp", it is sometimes difficult to determine which of the several units has the failing battery, and the owner may elect to either ignore the warning or change the batteries in all the system units, both unsatisfactory expedients.
It will therefore be appreciated that it would be desirable to provide a feature by which an individual unit in a multi-station dangerous condition alarm system can be identified as the originator of an alarm (which may be false) sounded by all the units or the originator of a low battery warning "chirp"sounded by the unit with a failing battery. In the former case, if the sounded alarm is determined to be false and the result of a defective unit, only that individual unit need be returned to the retailer or manufacturer for replacement, thus saving time and money for the owner, the retailer and/or the manufacturer while leaving in place the remainder of the units in fully operative condition. In the latter case, only the battery in the individual unit which originated the low-battery "chirp" need be replaced, thus saving time and money for the owner of the system.